Method of treating tobacco stalks

ABSTRACT

A method of treating tobacco stalks for use in tobacco cut filler comprises the steps of: breaking up the tobacco stalks to form tobacco stalk segments; conditioning the tobacco stalk segments to increase the moisture content; and rolling the tobacco stalk segments to form tobacco stalk flakes having a rolled thickness of between 0.05 millimetres and 0.5 millimetres. Preferably, during the rolling step, the tobacco stalk segments are rolled between two counter-rotating rollers rotating at different speeds to each other.

The present invention relates to a method of treating tobacco stalks for use in tobacco cut filler. It also relates to the production of cut filler comprising tobacco stalks that have been treated using such a method.

It is known that tobacco cut filler for smoking articles may be manufactured predominantly from the lamina portion of the tobacco leaf, which is separated from the stem portion of the leaf during a threshing process. In order to increase the amount of the tobacco material that can be used, it has also been previously proposed to add some tobacco stems back into the cut filler together with the lamina. However, the main stalk portion of the tobacco plant that remains after the tobacco leaves have been harvested from the plant is typically not used, since it has not been possible to find suitable methods of processing the tobacco stalk material to make it appropriate for use in cut filler. The stalk of the tobacco material is therefore not utilised and must be disposed of in an appropriate manner.

It would be desirable to provide a method for treating tobacco stalks so that they become more suitable for use as a blend component of cut filler for smoking articles. It would be particularly desirable if such a method could produce material from the tobacco stalks that can be processed together with the tobacco lamina. It would also be desirable to provide a method for treating tobacco stalks using conventional apparatus, therefore making it cost efficient to implement such a method.

According to the invention there is provided a method of treating tobacco stalks, the method comprising the steps of:

-   -   breaking up the tobacco stalks to form tobacco stalk segments;     -   conditioning the tobacco stalk segments to increase the moisture         content; and     -   rolling the tobacco stalk segments having a rolled thickness of         between 0.05 millimetres and 0.5 millimetres.

The method of the present invention produces tobacco stalk flakes which are suitable for use in tobacco cut filler.

In the present specification, the term “stalk” is used to refer to the main structural portion of the tobacco plant that remains after the leaves, including the stem and lamina, have been removed. The stalk supports the tobacco leaves and connects them to the roots of the plant and has a high cellulosic content.

The term “stem” is used herein to refer to the structural portion of the tobacco plant connecting the lamina to the stalk, and also to the veins or ribs that extend through the leaves between the lamina portions. In the context of the present invention, the term “stem” does not encompass the term “stalk” and the stems and stalk of the tobacco plant are considered as distinct portions.

The “rolled thickness” of the tobacco stalk flakes produced by methods according to the invention refers to the distance between a first surface of the tobacco leaf that has been contacted with a rolling apparatus and a second surface of the tobacco leaf that has been contacted with a rolling apparatus. For example, the “rolled thickness” of the rolled tobacco leaf may refer to the distance between an upper surface of the tobacco leaf and a lower surface of the tobacco leaf. The rolled thickness therefore corresponds to the dimension of the tobacco stalk segments that is reduced in size during the rolling process. The rolled thickness of an individual tobacco stalk flake can be measured using a conventional measuring device under a microscope. The rolled thickness of an individual stalk flake is taken at the point along the direction of cutting that yields the largest cross-sectional area.

It has surprisingly been found that subjecting the tobacco stalks to the treatment method of the present invention provides tobacco stalk flakes that have a similar appearance to the tobacco lamina used in cut filler and can contribute to the taste and aroma of the mainstream smoke. As a result, a proportion of tobacco stalk flakes can be incorporated as an acceptable component of cut filler together with tobacco lamina and optionally, tobacco stem segments.

The use of tobacco stalk flakes in place of the tobacco lamina in cut filler is cost effective, since the stalks are typically available at a lower cost than the tobacco lamina. The use of the tobacco stalk flakes also has a positive environmental impact, by improving the exploitation of the tobacco plant material and thereby reducing the amount of tobacco material that is wasted. Furthermore, the use of tobacco stalk flakes may be advantageous in the production of reduced nicotine products, due to the lower nicotine content of the tobacco stalks compared to the lamina.

Advantageously, the tobacco stalks can be processed using conventional apparatus and techniques. In addition, the resultant tobacco stalk flakes can be processed together with the tobacco lamina in existing primary processing lines. The costs of implementing the method of the present invention and incorporating the resultant tobacco stalk flakes into cut filler are therefore minimised.

In the method of the present invention, the tobacco stalks are effectively broken down in a series of steps to provide tobacco stalk flakes, which have a thickness that is close to that of tobacco lamina. Further, a tobacco product can be obtained that includes more stalk material and wherein stalk material blends more effectively with the lamina. The method of the present invention may be carried out on tobacco stalks from any type of tobacco plant, including but not limited to Burley tobacco, Virginia tobacco or Oriental tobacco. The method may be carried out on stalks from a single type of tobacco leaf or on stalks from a blend of two or more different types.

The method of the invention is carried out on tobacco stalks from which the tobacco leaves and stems have already been removed. In the first step of the method, the tobacco stalks are broken up to reduce their size in order to optimise the subsequent rolling process. The tobacco stalks may be broken up into tobacco stalk segments using any suitable method. Suitable methods to break up tobacco stalks include, but are not limited to, shredding, cutting, slicing, chopping, or slashing. Preferably, the tobacco stalks are broken up into tobacco stalk segments having a length of between about 10 millimetres and about 500 millimetres, more preferably between about 50 millimetres and about 100 millimetres.

In the context of the present invention, the term “length” refers to the dimension of the stalk in the direction of the main stalk axis. The tobacco stalk will typically be broken up along its length. Alternatively, or in addition to cutting the tobacco stalks along their length, the stalks may be broken up by cutting or splitting each tobacco stalk in a substantially radial direction, that is, towards the centre. This will decrease the transverse cross-sectional area of the stalk segments and expose the internal surfaces of the hollow tobacco stalks. Preferably, the tobacco stalks are broken up into tobacco stalk segments having a width of between about 5 millimetres and about 20 millimetres. Alternatively or in addition, the tobacco stalks are preferably broken up into tobacco stalk segments having a thickness of between about 1 millimetre and about 10 millimetres. The “width” and “thickness” of the tobacco stalk segments refer to the dimensions of the stalk segments perpendicular to the length, as defined above.

Optionally, the tobacco stalks may be conditioned to increase the moisture content prior to the step of breaking up the stalks. Preferably, during the optional conditioning step the moisture content of the tobacco stalk segments is increased to about 15 to 35 percent oven volatiles, more preferably to about 20 to 30 percent oven volatiles.

After the tobacco stalks have been broken up into tobacco stalk segments, the tobacco stalk segments are conditioned to increase the moisture content prior to rolling so that the stalks are sufficiently pliable to be rolled with minimal breakage, cracking or other damage occurring. The conditioning of the tobacco stalk segments may further facilitate the rolling of the segments to the desired thickness and may improve the appearance of the tobacco stalk flakes. Preferably, during the conditioning step the moisture content of the tobacco stalk segments is increased to about 15 to 35 percent oven volatiles, more preferably to about 20 to 30 percent oven volatiles.

The moisture content of the tobacco material is expressed herein as “percent oven volatiles”, which is determined by measuring the percentage weight loss from the tobacco stalks due to evaporation upon drying the material in an oven at 103 degrees Celsius for 100 minutes. The moisture content of the tobacco stalks can readily be determined at any stage of the treatment method using this process.

The conditioning of the tobacco stalk segments is preferably carried out by contacting the tobacco stalk segments with water, steam, or a mixture of water and steam. For example, the tobacco stalk segments may be contacted with a counter flow of steam and water while being tumbled in a rotating cylindrical drum. The tobacco stalk segments may alternatively be conditioned in a humidity chamber. In a further alternative, the tobacco stalk segments may be left to soak for a period of time in order to allow the moisture to penetrate into the internal structure of the stalks.

After the conditioning step, the tobacco stalk segments are rolled to reduce the thickness of the stalks to between about 0.05 millimetres and about 0.5 millimetres. The thickness of the tobacco stalk segments is reduced to a level that is close to the thickness of tobacco lamina. Preferably, the tobacco stalk segments are rolled to a thickness of between about 0.1 millimetres and about 0.2 millimetres.

By rolling the tobacco stalk segments to this thickness, the resultant stalk flakes are visually similar to tobacco lamina and can therefore be incorporated into cut filler without impairing the appearance of the cut filler. In many cases, the tobacco stalk flakes are visually indistinguishable from the lamina material. Furthermore, by matching the thickness of the tobacco stalk flakes to that of the tobacco lamina, the risk of the stalk flakes settling out from the remainder of the cut filler during transport or storage is minimised.

The rolling of the tobacco stalk segments to a thickness of between 0.05 millimetres and 0.5 millimetres at least partially breaks down the cellular structure of the stalk material and ruptures the plant tissue on a microscopic scale. The breakdown of the cellular structure of the tobacco stalks is clearly visible when the rolled tobacco stalks are viewed through a microscope.

Preferably, during the rolling step of the method of the present invention, the rollers apply a compressive force of at least about 50 tonnes to the tobacco stalk segments, more preferably at least about 70 tonnes. The rolling is preferably carried out in a single step rolling process, although in some cases a two step rolling process may be suitable. The gap between the rollers may be varied to achieve the desired rolled thickness of the tobacco stalk flakes.

Preferably, during the rolling step the tobacco stalk segments are rolled between a pair of counter-rotating rollers. In particularly preferred embodiments, the tobacco stalk segments are rolled between a pair of counter-rotating rollers that are rotating at different speeds to each other, that is, differential speed rollers. It has advantageously been found that the use of differential speed rollers facilitates the rolling of the tobacco stalk segments to the required thickness of between 0.05 millimetres and 0.5 millimetres. It is believed that this is due to the stretching of the tobacco stalk segments as a result of the shear force to which the segments are subjected as they pass through rollers that are travelling at different speeds to each other. In fact, if rolls rotate at approximately the same speed, the leaves are substantially subjected to a compressive force. On the other hand, with rolls rotating at different speed, the leaves are subjected to both compressive and shear loads. This stretching of the tobacco stalk segments occurring at the same time as the compression of the tobacco stalk segments optimises the rolling process and enables a greater overall reduction in the stalk thickness. Further, the use of differential speed rollers allows for a finer particle size output.

It has also been found that the use of differential speed rollers in the rolling step of the method of the present invention produces rolled tobacco stalk segments having an improved appearance that more closely resembles the tobacco lamina. This means that the tobacco stalk segments are not visually distinct from the lamina when incorporated into cut filler.

Preferably, the counter-rotating rollers are operated such that the differential in surface speed of the rollers is at least about 5 percent, more preferably at least about 8 percent. This means that the surface speed of the faster of the two rollers is preferably at least about 5 percent greater than the surface speed of the slower roller. Preferably, the differential in surface speed of the rollers is less than about 15 percent, more preferably less than about 10 percent.

Preferably, the rollers operate at an average surface speed of between about 3 metres per second and about 8 metres per second, more preferably between about 4 metres per second and about 6 metres per second and most preferably about 5 metres per second.

In alternative embodiments, the tobacco stalks may be rolled between a single roller and a substantially flat surface.

In certain embodiments, the method according to the invention may further comprise the steps of applying a casing solution to the tobacco stalk flakes and heating the tobacco stalk flakes with the casing solution applied.

The application of the casing solution may advantageously improve the taste and visual appearance of the tobacco stalk flakes. The casing solution may be applied to the tobacco stalk flakes using any suitable means, including for example, spraying. The casing solution is preferably an aqueous solution comprising sugar. Typically, sugar will be the main component of the solution although a suitable humectant, such as glycerine, may be added. Optional flavour components may also be incorporated into the casing solution, if desired.

During the heating step, the tobacco stalk flakes to which the casing solution has been applied are heated in order to bring about a reaction between the casing solution and certain components of the tobacco. This step is responsible for the main development of the flavours of the tobacco stalks which arises as a result of the reaction of the tobacco compounds with the sugar in the casing solution.

During the heating step, the tobacco stalk flakes are preferably heated to a temperature of at least about 50 degrees Celsius. The heating of the tobacco stalk flakes may be carried out using any suitable means. In preferred embodiments, the tobacco stalk flakes are heated by a stream of hot air within a dryer. The stream of hot air is preferably at a temperature of between about 70 degrees Celsius and about 140 degrees Celsius, more preferably around about 200 degrees Celsius, to bring the temperature of the tobacco stalk flakes up to the preferred temperature of at least 50 degrees Celsius.

After the heating step, the tobacco stalk flakes may be re-conditioned to increase the moisture content. This may be advantageous, for example, where a further cutting step is required, as described below, to ensure that the tobacco stalks are sufficiently pliable to be cut without damage or breakage. During the re-conditioning step the moisture content of the tobacco stalk flakes is preferably increased to at least about 20 percent oven volatiles.

Methods according to the invention may further comprise the step of cutting the tobacco stalk flakes to reduce the size of the segments to a suitable cut width for use in cut filler. Preferably, the cutting step is carried out after the reconditioning step described above. The cut width can be adjusted according to the desired use of the tobacco stalk flakes. For example, a smaller, finer cut width may be preferred for cut filler intended for use in smoking articles, in particular slim cigarettes, than for a roll-your-own or pipe tobacco product. Preferably, the tobacco stalk flakes are cut to a cut width of between about 0.3 millimetres and about 1.3 millimetres, more preferably between about 0.65 millimetres and about 0.9 millimetres.

After cutting, the tobacco stalk flakes may optionally be dried to reduce the moisture content. Preferably, the moisture content is reduced to between about 10 percent and about 15 percent oven volatiles, more preferably between about 12 percent and about 14 percent oven volatiles. The drying step may be carried out at room temperature, but preferably the tobacco stalk flakes are heated in a stream of hot air at a temperature of between about 70 degrees Celsius and about 200 degrees Celsius. Suitable apparatus for drying of the tobacco stalk flakes include but are not limited to a rotary dryer and a flash tower dryer.

The tobacco stalk flakes may optionally be combined with tobacco lamina at a particular stage during methods of the present invention such that one or more of the subsequent steps are carried out on the blend of tobacco stalks and tobacco lamina. In certain embodiments of the present invention, the tobacco stalk flakes are combined with tobacco lamina prior to the application of the casing solution such that all of the subsequent treatment steps are carried out on the combined tobacco stalk flakes and lamina. Alternatively, the tobacco stalk flakes could be treated separately on a different production line to the tobacco lamina, and the tobacco lamina and stalks could be blended together after treatment. Rolled tobacco stems may additionally be blended with the lamina and stalks if desired.

As described above, the rolling of the tobacco stalk segments to a thickness of between 0.05 millimetres and 0.5 millimetres allows the tobacco stalk flakes to be produced with similar dimensions to the tobacco lamina. This advantageously means that the blend of tobacco stalks and lamina can travel together through at least a part of the treatment apparatus and can conveniently be treated together in the same process steps and conditions, if desired. The processing of the tobacco material can therefore be carried out using existing apparatus which is already in use for the treatment of tobacco lamina. This provides an efficient and cost effective way of treating the blend of tobacco stalks and lamina without the need for additional apparatus.

The tobacco stalk flakes produced by the method of the present invention may advantageously be incorporated into cut filler products for use in smoking articles. The tobacco stalk flakes may be incorporated directly into the cut filler together with the lamina, or may be further processed, for example to form a reconstituted tobacco material, before being added back into the cut filler.

According to the invention there is provided a method for the production of cut filler comprising tobacco stalk flakes, the method comprising treating tobacco stalks in accordance with the method of the invention, as described above, and blending the resultant tobacco stalk flakes with tobacco lamina.

The present invention further provides a tobacco cut filler for a smoking article comprising at least about 0.5 percent by weight of tobacco stalk flakes having a rolled thickness of between 0.05 millimetres and 0.5 millimetres. Preferably, the tobacco cut filler comprises at least about 1 percent by weight of the tobacco stalk flakes. Preferably, the tobacco cut filler comprises no more than about 30 percent by weight of the tobacco stalk flakes, more preferably no more than about 10 percent by weight. For example, in preferred embodiments the tobacco cut filler includes between about 0.5 percent by weight and about 30 percent by weight of the tobacco stalk flakes, or between about 1 percent by weight and about 10 percent by weight.

At this level, the inclusion of the tobacco stalk flakes in the cut filler will have a virtually undetectable effect on the taste of the cut filler into which the rolled tobacco stalk segments are incorporated. The tobacco stalk flakes are blended with at least one type of tobacco lamina, expanded tobacco, reconstituted tobacco or combinations thereof to provide the cut filler. The tobacco lamina may include for example Burley tobacco lamina, Oriental tobacco lamina, flue-cured tobacco lamina, or a combination thereof. The expanded and reconstituted tobacco, where present, may be formed of any suitable tobacco type using known apparatus and methods.

The blending of the tobacco stalk flakes with the other types of tobacco material may take place prior to the cutting and drying steps, so that the final blend is cut and dried together in the same batch. Alternatively, the blending may take place after the cutting and drying have been carried out on the tobacco stalk flakes, so that the blending is the final step in the production of the cut filler.

Tobacco stalks treated by methods according to the invention may be incorporated into a variety of smoking articles. In particular, tobacco stalks treated by the methods according to the invention may be incorporated into smoking articles as such or after having undergone one or more other operations, such as a treatment with a casing solution. In some embodiments, tobacco stalks treated by methods according to the invention find application for the production of a cut filler that may be used in the tobacco rod of a combustible smoking article, such as a filter cigarette, cigarillo or cigar. Alternatively, the cut filler may be used to provide the tobacco aerosol generating substrate in a distillation based smoking article, or an electrically heated smoking system. Alternatively, the cut filler may be used as a roll-your-own or make-your-own product, or loose tobacco product for use in a pipe.

Smoking articles comprising cut filler including tobacco stalks treated using methods according to the invention may be packaged in containers, for example, containers formed of one or more folded laminar blanks. Suitable containers include but are not limited to hinge lid containers and slide and shell containers.

The invention will be further described, by way of example only:

Example

A method according to the present invention is carried out on tobacco stalks from which the leaves have mostly been removed. In this context, the expression “mostly removed” is used to mean that, after the stems are cut off, small portions or stumps of the stems may still be present.

The stalks are first broken up to produce stalk segments having a length of less than 500 millimetres.

In the conditioning step, the tobacco stalk segments are placed into a cylindrical drum which is rotated to continuously move the stalk segments. A counter flow of steam and water is passed through the cylinder into contact with the tobacco stalk segments until the moisture content of the tobacco stalk segments reaches approximately 30 percent oven volatiles.

The conditioned tobacco stalk segments are then rolled between counter-rotating rollers to a rolled thickness of 0.15 millimetres to produce tobacco stalk flakes. The rollers are operated with a differential speed of 8 percent and apply a compressive force of 80 tonnes.

The tobacco stalk flakes are then sprayed with a casing solution of sugar in water. In addition to the sugar, the casing solution includes glycerine, which acts as a humectant.

After the casing has been applied, the tobacco stalk flakes are then heated in an apron dryer for four to eight minutes with hot air at a temperature of approximately 100 degrees Celsius so that the temperature of the tobacco is increased to approximately 50 degrees Celsius.

After the heating step, the tobacco stalk flakes are cooled and re-conditioned using a similar method and apparatus to the conditioning step described above, until the moisture content of the tobacco stalk segments is brought back to approximately 20 percent oven volatiles.

The treated tobacco stalk flakes are then mixed with other tobacco materials, including tobacco lamina, to form the cut filler blend.

The cut filler blend including the tobacco stalk flakes is then cut with blades set at a standard cut width of 0.9 millimetres and subsequently dried to a moisture level of around 13 percent oven volatiles before being transferred to storage, or directly to a cigarette manufacturing line.

It will be appreciated that the moisture levels, rolled stalk thickness, cut width, proportion of tobacco stalks and other parameters of the treatment process may be varied, as described above, depending upon the desired characteristics and intended use of the final cut filler. 

1. A method of treating tobacco stalks, the method comprising the steps of: breaking up the tobacco stalks to form tobacco stalk segments; conditioning the tobacco stalk segments to increase the moisture content; and rolling the tobacco stalk segments to form tobacco stalk flakes having a rolled thickness of between 0.05 millimetres and 0.5 millimetres.
 2. A method according to claim 1 wherein during the rolling step the tobacco stalk segments are rolled between two counter-rotating rollers rotating at different speeds to each other.
 3. A method according to claim 2 wherein the differential in surface speed of the pair of counter-rotating rollers is at least 5 percent.
 4. A method according to claim 1 wherein the tobacco stalks are broken up to form tobacco stalk segments having a length of between 10 millimetres and 500 millimetres.
 5. A method according to claim 1 wherein during the conditioning step the moisture content of the tobacco stalk segments is increased to 20 to 35 percent oven volatiles.
 6. A method according to claim 1 wherein the conditioning step comprises contacting the tobacco stalk segments with steam, water or a mixture of steam and water.
 7. A method according to claim 1 wherein during the rolling step a compressive force of at least 50 tonnes is applied to the tobacco stalk segments.
 8. A method according to claim 1 further comprising the steps of: applying a casing solution to the tobacco stalk flakes; and heating the tobacco stalk flakes with the casing solution applied.
 9. A method according to claim 8 wherein the tobacco stalk flakes are re-conditioned after heating in order to increase the moisture content.
 10. A method according to claim 8 wherein the tobacco stalk flakes are combined with tobacco lamina prior to the application of the casing solution such that the subsequent steps are carried out on the combined tobacco stalk flakes and lamina.
 11. A tobacco cut filler obtained by a method comprising breaking up the tobacco stalks to form tobacco stalk segments; conditioning the tobacco stalk segments to increase the moisture content; and rolling the tobacco stalk segments to form tobacco stalk flakes having a rolled thickness of between 0.05 millimetres and 0.5 millimetres.
 12. A tobacco cut filler method according to claim 11 wherein during the rolling step the tobacco stalk segments are rolled between two counter-rotating rollers rotating at different speeds to each other.
 13. A tobacco cut filler according to claim 12 wherein the differential in surface speed of the pair of counter-rotating rollers is at least 5 percent.
 14. A tobacco cut filler according to claim 11 wherein during the conditioning step the moisture content of the tobacco stalk segments is increased to 20 to 35 percent oven volatiles.
 15. A tobacco cut filler according to claim 11 comprising at least 5 percent by weight of tobacco stalk flakes.
 16. A method according to claim 9 wherein the tobacco stalk flakes are combined with tobacco lamina prior to the application of the casing solution such that the subsequent steps are carried out on the combined tobacco stalk flakes and lamina.
 17. A tobacco cut filler according to claim 12 wherein during the conditioning step the moisture content of the tobacco stalk segments is increased to 20 to 35 percent oven volatiles.
 18. A tobacco cut filler according to claim 13 wherein during the conditioning step the moisture content of the tobacco stalk segments is increased to 20 to 35 percent oven volatiles.
 19. A method according to claim 3 wherein the tobacco stalks are broken up to form tobacco stalk segments having a length of between 10 millimetres and 500 millimetres.
 20. A method according to claim 19 wherein during the conditioning step the moisture content of the tobacco stalk segments is increased to 20 to 35 percent oven volatiles. 